1. Technical Field
The present invention relates to a cooling device for an internal combustion engine, a thermostat device, and more particularly, to a thermostat device that can be mounted as a single unit at a predetermined location near the engine, for example, without being imbedded in an engine constituent member such as the engine block, etc.
2. Description of the Background Art
Most cooling systems for vehicle internal combustion engines currently on the market cool the engine using a water-cooled system employing a coolant as the medium. In addition to 4-wheeled vehicles, this type of water-cooled cooling system is also widely employed in 2-wheeled vehicles as well.
The above-described water-cooled cooling system employed in internal combustion engines for vehicles has a radiator provided external to the engine. The radiator and the engine are connected by a rubber hose and the coolant is circulated between the radiator and the engine. The system is constructed of the radiator, which acts as a heat exchanger; a water pump, which forcibly pumps the coolant from the radiator to the engine; a thermostat that controls the flow of coolant based on the temperature of the coolant flowing from the radiator or flowing to the radiator to maintain the coolant at the proper temperature; and the rubber hose, which forms a circulation flow path for the coolant. The system prevents the engine from overheating while at the same time prevents the engine from overcooling during cold weather, and works always to maintain the engine at the proper temperature.
However, the applicant has already proposed a thermostat device for use in this type of water-cooled system in which the thermostat device is an externally mounted thermostat device that is mounted externally at a particular place such as the outside of the engine head (not shown), and moreover configured as a single unit housing the thermostat (i.e., a valve) (see, for example, JP-2006-342767-A).
In this conventional device, a thermo-element is inserted inside a casing and biased by a return spring, and in that state the casing is capped with a cap and the casing and the cap are then lasered or otherwise welded together.
In this type of thermostat device, a construction in which a temperature sensor that detects the temperature of the cooling water that flows through the interior of the device containing the thermostat has been proposed (see, for example, JP-2003-222264-A). In this conventional device, the temperature sensor is provided at a position where it does not project beyond a supporting step portion projecting from the inner wall of the casing so that the temperature sensor does not interfere with installation of a frame that seats the spring.
However, the thermostat device of JP-2006-342767-A experiences the following problem upon insertion of the temperature sensor described in JP-2003-222264-A.
That is, in this type of conventional device, the overall construction of the device becomes complicated, the number of constituent parts increases, and assembly becomes difficult. In particular, when it comes to installing the temperature sensor, where to insert the sensor becomes a problem, and what was once easy assembly becomes difficult and complicated.
Further, with this type of conventional device, it is desirable that the device have the least complicated structure possible and that it be capable of being made small and compact.